Electric illumination control system



Au 30, 1938. R. B. llUNTER I 2,128,361 ELECTRIC ILLUMINATION CONTROLSYSTEM Filed Dec. 24,1954 2 Sheets- Sheet 1 Aug. 30, 1938 R. B. HUNTER OELECTRIC ILLUMINATION CONTROL SYSTEM Filed Dec. 24-, 1934 2 Sheets-Sheet2 TIME Patented Aug. 30, 1938 Richard B. Hunter, Shorewood, Wis.,assignor to Cutler-Hammer, Inc. poration of Delawar- Milwaukee. -Wis., acor- Application December 24, 1934, sci-mine. 758,960 4 14 Claims.

This invention relates to electric illumination control systems and moreparticularly to systems and apparatus for controlling the degree ordegrees of energization of electric illumination cir-' 5 cuits.

While not limited thereto the invention is 'particularly applicable tothe control of illuminating lights wherein it is desired to eifect'regularly recurring illumination intensity variations of a predeterminedcharacter. A

An object of my invention is to provide control systems of theaforementioned character having means for individually preselecting theminimum intensities and the maximum intensities of iilumination of therespective groups of lamps.

Another object is to provide such apparatus having means-forindividuallypreselecting the rates of increase and the rates of decreasein intensities of illumination of' the respective groups of lamps.

Another object is to provide such apparatus having means forautomatically varying the intensities of illumination of a plurality ofgroupsof lamps between selected minimum and maximum values in accordancewith selected rates of increase and decrease of such intensities,respectively.

Another object is to provide a plurality of units of apparatus'of theaforementioned character having meanswhereby the phase relation of thecyclic illumination intensity changes in the respective groups of lampsmay be preselected. Another object is to provide means common to therespective control units of a plurality of lamp circuits forautomatically rendering the aforementioned illumination varying meanseffective at regularly recurring intervals.

Various other objects and advantages of the invention will hereinafterappear.

In carrying .out my invention I prefer to em- 55 in Figs. 1 and 2.

circuits employing differently colored groups of The contact arms"! and8 are manually adjust- "control parts shown in Figs. land 2.

Fig. 4 is a diagram showing the operation of the light circuits of Figs.1 and 2 under given conditions of adjustment of the control systems, and

Fig. 5 is a fragmentary diagrammatic illustration of amodifled'arrangement of certain of the 5 Referring first to Fig. 1 ofthe drawings, I have illustrated, by way of example, two groups ofelectric lamps, designated respectively by the reference characters] and2, continuity of cir- 10 cuitand intensity of illumination ofv the lampsin the respective group's beihg subject to control by a systemconstructed in accordance with my invention; it'being" understood thatin practice a considerably larger number of lamp groups. will '15ordinarily be employed, the control elements being merely duplicated foreach additional group of lamps, as'will be pointed out more clearlyhereinafter.

, Included in circuit with the lamps of group I isa suitable currentcontrolling or regulating devlce,'such as the dimmer rheostat 3. Amanually-operable switch 4 is also included in circuit with thelamp's ofgroup 1 to provide for connection of the lamps across lines L, L

Upon closure of the switch 4' the circuit for the l'amp-group'l will becompleted, the intensity, of illumination of the lamps being dependentupon the position of the rheostat contact arm 5 of the dimmer rheostat3. Said contact arm is shown in its lower extreme position and isadapted to be moved between said position and its upper extreme positionto provide for gradual variation of the illumination intensity of thelamps between full-dark and full-bright illumination intensity.

Means-are provided to effect movement or adjustment of therheostatwontact arm 5 from any given position thereof to any otherposition preselected therefor. More specifically, the meansaforementioned provides for automatic movement of said, rheostat armalternately in opposite directions between preselected positions. .Themeans for preselecting the positions between which the rheostat arm 5 isto be moved and for effecting movement of. said arm eomprisesessentially a sending rheostat 6, having adjustable contact arms I and 8associated therewith, a receiving rheostat 9 having an adjustablecontact arm l0 associated therewith, and the coil Ii of a polarizedrelay of suitable form, said rheostats 6 and 9 and coil II beingconnected with respect to each other and with respect to lines L, L inthe form of a Wheatstone bridge.

through one pole of the switch i8, armature A able, the pivoted ends ofsaid arms being connected selectively to one side of the polarized relaycoil ii through the normally closed contacts i2 and the normally opencontacts ll, respectively, of an electromagnetically operable switch H.The other side of the coil Ii is connected to the pivoted end of thepower-operated contact arm ill. r

The contactor I5 of the polarized relay is normally biased to anintermediate or neutral position, as illustrated, when the bridgecircuit is in balanced condition, and the same is moved automaticallyinto engagement with the stationary contacts I6, i'l, selectively,depending upon the direction of unbalance of the bridge circuit. Thecontrolling effect of the Wheatstone bridge circuit and its associatedparts is described in detail in my Patent No. 1,906,859, dated May 2,1933.

The operation of the control system illustrated in Fig. 1 is as follows:

Assuming that the various elements of the control system are in therespective positions illustrated and that it is desired to provide agiven illumination or lighting effect, the switch 4 is closed to connectthe lamp group I across the lines L, L which represent a suitable sourceof alternating current supply.

Closure of the switch l8 connects the Wheatstone bridge circuit acrosslines L L, which represent a suitable source of direct current supply.Upon energization of the bridge circuit the rheostat contactor 5 willeither remain in its lower extreme position or will be moved to vary theamount of resistance of rheostat 3 in circuit with the lamps, asdetermined by the relative positions of the contact arms 1, 8 and ill.The contactor 5 and the contact arm ID are shown as being mechanicallyconnected with but electrically insulated from each other.

The contact arm 1 is shown as having been adjusted to a positionslightly above its lower extreme position, thus providing for arelatively low intensity of illumination as the minimum intensity atwhich it is desired that the lamps of group I shall burn to obtain agiven'lighting effeet. The contact arm 8 is shown as having beenadjusted to a position which provides for substantially three-fourthsbright illumination intensity as the maximum intensity at ch it isdesired that the lamps of group i sh ...,:-:burn.

Thus upon closure of switch I! the Wheatstone bridge circuit will beenergized, the circuit extending from line L through one pole of theswitch l8, a small portion of the sending rheostat contact arm 1,normally closed contacts l2 of switch ll, through the polarized relaycoil ll, contact arm Ill, through all of the receiving rheostat 9, andthrough the other pole of switch l8 to line L. The bridge circuit willbe unbalanced due to the difference in the relative positions of thecontact arms 1 and I0, consequently the direction of current flowthrough the coil II will be such as to move the contactor l5 into en-'gagement with the stationary contact I, establishing for the motorswitch l9 an energizing circuit extending from line L through one poleof switch I8, winding of switch i9, contact II and contactor l5 of thepolarized relay, and through the other pole of switch l8 to line L.

Switch l9 responds to establish for the motor M an energizing circuitextending from line LP and field F of said motor, through a portion ofrheostat 20, contact arm 2|, switch I! and through the other pole ofswitch It to line 13 whereupon the motor M operates in a direction tomove the contact arm in through the medium of the gear drive 35 upwardlyon the receiving rheostat 9 into a position-corresponding to that of thecontact arm I on the rheostat 6, thus balancing the bridge circuit anddeenergizing motor M. Contactor 5, being mechanically connected to thecontact arm III, is moved into a position on the dimmer rheostat 3wherein a relatively low intensity of illumination of the group of lampsl is provided. I

Motor M is provided with a second field F adapted upon energizationthereof to effect operation of the motor in the reverse direction.Included in circuit with the aforementioned field F is the rheostat 20the contact arm. 2i of which is shown as having been adjusted to provideior inclusion of substantially three-fourths of the resistance of saidrheostat in circuit with said held for effecting operation of the motorat a relatively low speed. Included in circuit with the field F is theelectromagnetically operated switch 22 and the rheostat 23, the contactarm 24 of which is shown as having been adjusted to provide forinclusion of substantially half of the resistance of the rheostat 23 incircuit with the field F. It will be readily apparent from the foregoingthat the speed of movement of the contactor 5 in each direction over thedimmer rheostat 3 is controlled by adjustment of the respective rheostatcontact arms 2| and 24.

Means common to the various groups of lamps such as groups I and 2 areprovided to effect alternate energization and deenergization of theswitches H at predeterminedintervals,whereby,as will be more clearly setforth in connection with lamp group I, the contact arms 1 and 8 arealternately rendered effective, causing unbalancing of the Wheatstonebridge circuit in opposite directions with consequent movementof thecontactor 5 between positions on the dimmer rheostat 3 which correspondto the positions of the arms] and B on the sending rheostat 5.

The aforementioned cycling means comprises a set of normally opencontacts 25 to 34, inclusive, which areadapted to be closed successivelyby the cams 35 to 45, inclusive. Said cams are fixed to a shaft 48 whichis arranged to be driven by the motor 41 through the medium of the speedreducing gear driye' l8.

Associated with each of the groups of lamps i and 2 is a selector 50 and5|, respectively. Each of said selectors comprises a number ofstationary contacts 52 to SI, inclusive, said contacts being connectedto the contacts 25 to 3, respec tively, of the cycling means. Thecontacts 52 to Bl of the selector 50 are arranged to be engagedselectively by the contactors '62 and 63, said contactors being manuallyadjustable to provide for control of the time at which the increase andthe decrease, respectively, in illumination intensity of the lamps isinitiated Upon closure of the switch the motor 41 is connected acrosslines L, L? and operates to drive the shaft in a clockwise direction (asindicated by the arrow) through the medium of the gear drive ll. The cam36 is shown as having eiiected closure of the contacts 25 and as theshaft 45 continues to rotate the cams 31 to 45 effect closure"successively of the contacts 25 to 3!. The

:contactor 82 of the selector 50 is shown in encontacts 26, contact 53and contactor 82 of selector 50, through the winding of switch I4 andthrough resistance 64 to line L.

the contact arm 8 of sending rheostat 6, contacts 65 of switch I4 alsobeing closed and contacts I2 .thereof being opened. The Wheatstonebridge circuit will be unbalanced, the circuit therethrough extendingfrom line L through one pole of switch I8, a portion of rheostat 6,contact arm 8, contacts I3 of switch I4, polarized relay coil II,contact arm III, which, as aforestated, will as aforedescribed. Responseof switch I8 effects have moved to a position corresponding to theposition of contact arm "I, through a portion of the receiving rheostat9 and through the other pole. of switch I8 to line L.

Contactor I5 of the polarized relay will move .-into engagement with thestationary contact I8,

due to unbalancing of the bridge circuit, to establish for the motorswitch I9 an energizing circuit I to substantially three-fourths fullbrightness thereof.

The circuit for the winding of switch I4 is maintained through contacts55 of said switch:

Thus the maximum illumination intensity of the lamps of group I, asdetermined by the position of contact arm 8, is maintained until motor41 has rotated shaft 48 far enough to effect closure of contacts 32 bycam 43, whereupon the winding of switch I4 is short-circuited, as isreadily apparent. Switch I4- drops out to open the contacts I3' and 85and to close the contactsv I2. Contact arm I again becomes effective andthis time the bridge circuit becomes unbalanced in the oppositedirection. Polarized relay con-' tactor I5 will be moved, intoengagement with stationary contact I I to establish for motor switch 22an energizing circuit extending from line L through one pole of switchI8, the winding of switch 22, contact I I and contactor I5 of thepolarized relay, through the other'pole of switch I8 to line L Motorswitch 22 responds to complete a circuit for energization of motor Mextending from line I through one pole of switch I8, armature A andfield F of said motor, through a portion of rheostat 23, contactor 24,switch 22 and the other pole of switch I8 to line L. Motor M operates ina direction to eflect movement of contact arm I downwardly into aposition corresponding to that 01' contact arm I, and at a speeddetermined by' the setting of contact arm 24.

Thus contactor is moved over rheostat 8 to decrease the intensity ofillumination of the lamps of group I to a value determined by thesetting Response. ofswitch I4 closes contacts I 3 to render effectiveoperation, rendering it extremely, convenient to work out a pleasingcombination series or cycle of illumination eifects.

Now considering the lamp group 2, the adjustable elements of the controlunit associated.

therewith are shown adjusted to positions differing from those ofthe'elements associated with the lamp group I. Contact arm 61 of thesending rheostat 65 is shown in a position which provides forsubstantially one-fourth bright illumination intensity of the lamps,while contact arm 68 is shown in a position which provides forsubstantially seven-elghts bright illumination intensity of said lamps.vContact arm 88 of motor rheostat I0 is shown in a position whichprovides for a relatively rapid increase in illumination intensity ofthe lamps of group 2', while contact arm II of motor rheostat I2 isshown in a position which provides for a relatively slow or gradualdecrease in illumination intensity of said lamps.

As aforestated, contacts 52 to SI of selector 5I are electricallyconnected to the contacts 25 to 34, respectively. For purposes ofillustration the wires connecting said contacts are shown as beingcontained in a conduit I5. Said conduit is indicated as extending beyondthe selector 5| inasmuch as the contacts of selectors associated withadditional lamp circuits may be electrically connected to the contacts25 to 34 through the medium of the wires contained in said conduit, aswill be apparent.

Selector 5| has associated therewith contact arms 13 and I4. Contact arm13 is shown as having been moved into engagement with stationary contact55, which contact is electrically connected with'the stationary contactof the aforementioned set 28. Thus when closure of contacts 28 iseffected by cam 39 contact arm 68 of sending rheostat 81 will berendered eifective with results similar to those aforedescribed in.

connection with the lamp group I. Contact arm 14 is shown as having beenmoved into engagee ment with contact 60, which contactis electricallyconnected with the stationary contact 'of set 33. When closure ofcontacts 33 is effected by cam 44 contact arm 81 will be renderedeffective with results similar to those aforedescribed in con'- nectionwith the lamp group I.

The control elements of the aforedescribed system are preferablyarranged upon a control panel in a manner to provide for convenientarrangement of the manually operable elements of the system upon theface of said panel. For example, a portion of such a control panel isillustrated at 18 in Fig. 3,v showing the arrangement of the manuallyadjustable contact arms associated with the control units for threegroups of lamps. The handles of the contact arms .1, 8, 2 I, 24, 52 and63 associated with the lamp group I,

1 are shown as comprising the group at the lefthand side of the panel;the group of handles in the center of the panel comprise those of thecontact arms 81, 88, 58, II, 13 and 14, associated' with the group oflamps 2. The group of handles at the right-hand side of the controlpanel comprise those of contact arms II. to 82, inclusive,

associated with an additional group of lamps lighting effects willbeproduced of substantially the character illustrated diagrammatically inFig. i. It may be assumed that the lamps in each of thegroups I and 2and the lamps in the group associated with the contact arms I! to 02 areof diil'erent colors. For example, the lamps of group I may be white,the lamps of group 2, red, and the lamps of the group with which thecontact arms 11 to 02 are associated may be blue, as indicated by theletters, W, R and B in Fig. 4, which designate the respective lightingcurves of the individual illumination circuits.

One division of the "time scale indicated in Fig. 4 represents theinterval between closure of two successive cam switches 20 to 24. Thuswith ten cams as illustrated in Fig. l a complete cycle of theillumination control is represented by ten divisions on the "time"scale. Referring to the curve W it will be noted that the rise in thecurve, representing voltage increase, begins at the second moment of the"time scale which is determined by the position of contact arm 62 ofselector 00. The rise of the curve W indicates a relatively gradualincrease in voltage as provided for by the setting of the contact arm IIon the motor rheostat 20. The fall in the curvew, representing voltagedecrease, begins at the eighth moment of the "time" scale as determinedby the position of contact arm 41 of selector 50. The rate of voltagedecrease, as aforedescribed, is determined by the setting of contact arm2'. of motor rheostat 21.

The curves R and B portray respectively, the voltage characteristics ofthe lamps of group 2 and the lamps of the group controlled by thecontact arms I1 to 02, as determined by the illustrated settings of thecontact arms associated with each group. Due to the setting of thecontact arms I9 and 14, l1 and II the cycles of illumination control ofthe latter groups of lamps, as portrayed by curves R and B.respectively, are out of phase with the cycle portrayed by curve W andout of phase with each other.

Referring to Fig. 2, the voltage of the lamps of groups I and 2 iscontrolled through the medium of the saturable reactors 90 and III,respectively. The lamps are connected across lines 'L and U, the lampsof group I being connected in series with the alternating current coils92 of the saturable reactor 90 and the lamps of group .2 being connectedin series with the alternating current coils 93 of the saturable reactorII. The reactors 90 and 9| are provided with the direct current controlwindings 94 and 95, respectively, each of said windings being connectedin series with an electron tube 99 across the lines L and L. Each of thereactor control windings 94 and 95 has connected in parallel therewithan electron tube 91, the purpose of which is to smooth out the ripplesof the current inthe windings as supplied through the tubes 00. v

Associated with each of the lamp groups I and 2- is a transformer 90having a primary winding 90! connected in'parailel with the lamps. Oneterminal of the secondary winding is connected with the control grid oftube 90 and the other terminal is connected with the anode 09* of adouble anode electron tube 99. The cathodes of tubes 90, 91 and 00 maybe heated in any wellknown manner. A second transformer I00 has aprimary winding I00 which is adapted to be connected selectively throughthe normally closed contacts I02 of a switch IIII with the pivoted endof contact arm I or through the normally open contacts I02 of saidswitch (when closed) with the pivoted end of contact arm 0.

Contact arms 1 and I are associated with a rheostat I01 and are employedas described in connection with Fig. 1 to pre-select'the minimum andmaximum intensities of illumination at which cuit consisting of acondenser I08 and a resistor I09 connected in parallel therewith. Asecond energy storage discharge circuit consisting of a condenser H0 anda parallel resistor III is connected in series with the secondarywinding I00" of transformer I00 between anode 99 and the cathode of tube99.

In accordance with the teachings of the patent of Carroll Stansbury, No.2,024,838 dated Dec. 17, 1935, additional energy storage dischargecircuits are provided as indicated by the numerals H2, H3, H4 and H5.Each of the last-mentioned circuits preferably possesses predetermineddischarge characteristics diifering from any of the other of saidcircuits in order to provide various rates of increase and decrease inillumination intensity of the lamps.

By means of the contact arms 2I and 24 and the stationary contacts H6,H1, H9, H9, I20 any one of the energy storage discharge circuits I I2,III, I I4, I I may be selectively connected in parallel with the energystorage circuit consisting of the condenser I I0 and the resistor I I Ito modify the discharge characteristic thereof as described in detail inthe aforementioned Stansbury patent.

The cycling means comprising the cam operated switches 25 to 34 andassociated mechanism, and the selectors 50 and 5| are essentiallyidentical with the corresponding devices shown in Fig. 1. Thusconsidering operation of the system controlling the illuminationintensity of the lamp group I as shown in Fig. 2, closure of switch 4will connect the lamps across lines L, L. Said lines represent analternating current constant potential source of supply. Closure ofswitch 49 connects motor 41 across lines L, L". Said motor drives shaft46 to -eifect closure of switches 25 to 34 successively, asaforedescribed. Contact arm 02 of selector 50. being in engagement withthe stationary contact 53 completes an energizing circuit for switch IOIupon'closure of contacts 29 of the timing means. Switch IOI responds toclose its contacts I03, I05 and I06 and to open its contacts I02 andI04. Closure of contacts I04 provides a maintaining circuit for switchI0 I.

Closure of contacts I03 renders effective the contact arm 8 of rheostatI01 while closure of contacts I05 renders effective the contact arm 2 I,whereupon energization of winding 94 of reactor 90 is increased to avalue determined by the setting of contact arm 8 and at a rate modifiedby the characteristics of the energy storage discharge circuit II3. Asis well known, variations of the current in the winding 94 producevariations in the voltage drop'across the coils 92 with consequentvariations in the value of current supplied to the lamps.

The maximum intensity of illumination of the lamps of group I ismaintained at the value determined by the setting of contact arm 8 untilcontacts 32 of the timing means are closed, with consequentshort-circuiting of the winding of switch I0 I. Closureof contacts I02renders contact arm I effective while closure of contacts I04 renderscontact arm 24 eifective. The current in winding 94 will be decreased toa value determined by the setting of contact arm 1 thus reducing theintensity of illumination of the lamps. The rate of decrease of currentin winding 94 is modified by the characteristics of the dischargecircuit I ll.

The minimum illumination intensity of the lamps will be maintained atthe value determined by the set ting of contact arm 1 until con- 'tacts2B of the timing means are again closed.

The foregoing cycle of control will be automatically repeated so long asthe system is energized.

As stated in the aforementioned Stansbury Patent No. 2,024,838,,thedesign of the' circuits H2, H3, H4, H5 depends upon'the desired rate ofchange in illumination intensity. Obviously,

the flexibility ofsthe system may be increased by the addition ofcircuits similar to circuits H2, I H,

H4 and H5, it being understood that for each circuit thus added anadditional contact corresponding to contacts I Hi to I20 will berequired.

In the system illustrated in Fig. 2, contact arms I and 8 of rhcostatI01, contact arms 61 and 68 of rheostat l 2 l contact arms 62 and 53 ofselector 5!] and contact arms 13 and 14 of selector 5| are shown incontrol positions corresponding to those of the corresponding contactarms associated with the system illustrated in Fig. 1. It may be assumedthat the control positions in which contact arms 21 and 24, 69 and H areshown in Fig. 2. provide for rates of illumination intensity in--invention herein disclosed the general characteristics of theillumination cycle with reference to time may be varied either byproviding means for. varying the speed of motor t! or by substituting asuitable variable speed transmission for the gearing i8.

If it is desired to vary the illumination in tensity between severalmaxima and minima during one complete cycle as provided by sequentialoperation of all of the cams 36 to 45, inclusive, the contacts 25 to 34,inclusive, controlled thereby may be interconnected electrically in themanner shown in Fig. 5, for instance, to provide for repetition of anygiven illumination effect two or more times during each revolution ofthe cam shaft 46. By this means I am enabled to stand-= ardize on thereduction gearing employed and upon the number of cams employed,regardless oi the number of illumination intensity variations desired inone control cycle, such means providing for changing the periods ofvariationin one direction or the other at will to suit the requirementsof each particular installation.

The arrangement shown in the fragmentary diagram, Fig. 5, includes onlythe three stationary contacts of the cam operated sets 25, i6, 21 for,

purposes of illustration. Each of said contacts has connected thereto ajack receptacle 25 26 Zi etc., and a plug jack 25 26 27', etc., it

the contacts '52- to El of selector 50 which are engaged by thecontactors 62 and $3. It is to bennclerstood that with the arrangementjust described each of the conductors connecting the contacts '52 to 6|of selector 5| to said contacts 25 to 34 would also be provided with ajack receptacle and a plug jack.

I also desire to point out that by providing additional contactors likethose designated by the numerals 62 and E3 (of selector 50) I mayincrease the number of illumination intensity changes for any circuitduring each revolution of shaft 46 while providing a smaller number ofillumination intensity changes for any other circuit during suchrevolution of said shaft 46.

In connection with the control system illustrated in Fig. 2, it is to beunderstood that the lighting curves shown in the diagram, Fig. 4,

while retaining substantially the outline there illustrated, will bemodified as described and illustrated in the aforementioned StansburyPatent- 1. In an illumination control system, in combination, a group ofelectric lamps, illumination intensity regulating means for said lamps,means for operating said regulating means between limits determining theminimum and maximum values of intensity of illumination of said lamps;said last mentioned means comprising a sending impedance and a receivingimpedance connected in parallel in the form of a Wheatstone bridge, thebalance of which determines the said limits of operation of saidregulating means, said sending impedance having a pair of elements whichare selectively effective eachto determine a point of balance of saidbridge, whereby to select a minimum and a maximum intensity ofillumination, respectively, for said lamps, associated means operable byunbalance of said bridge automatically to restore balance of said bridgeat one or the other of said points depending upon which of said elementsis effective, and simultaneously to operate said regulating means toprovide for sequential and gradual decrease or increase in the intensityof illumination of said lamps; means as-- soclated with the last namedrestoring-means to render the same operative at a predetermined rateduring said decrease of intensity of illumination and at asecond'predetermined rate during said increase of intensity ofillumination, and power operated means to respectively time initiationof the decrease and the increase in said intensity of illumination withreference to a given cycle by rendering one or the other of saidelements effective.

2. In an illumination control system, incoming a sending rheostat and areceiving rheostat arranged in the form of a Wheatstone bridge, a

contactor associated with said receiving rheostat and adapted to bedriven in opposite directions by said motor, said sending rheostathaving a pair of contactors each adjustable individually to de- 'terminea point of balance of said bridge, whereby to preselect the limits ofmovement of said receiving rheostat contactor and said impedance elementin opposite directions respectively, means for rendering said sendingrheostat contactors effective alternately for predetermined periods oftime with reference to a given cycle, means responsive to unbalance ofsaid bridge to selectively establish power connections for said I motorto effect operation thereof in one direction or the other and tending torestore balance of said bridge at one or the other of said pointsdepending upon which of said sending rheostat contactorsis effective,and simultaneously to move said impedance element to provide forsequential and gradual decrease or increase in the intensity ofillumination of said lamps, and means to preselect the speeds of saidmotor for each direction or operation thereof. s

3. In an illumination control system, in combination, a group ofelectric lamps, illumination intensity regulating means for said lamps,said means comprising a resistance element and a contactor movable withrespect to said resistance element, a reversible electric motor foreilecting movement of said contactor in opposite directions, follow-upcontrol means for said motor comprising a sendingrheostat and areceiving rheostat connected in the form of a Wheatstone'bridge, acontactor associated with said receiving rheostat and adapted to bedriven in opposite directions by ,said motor, said sending rheostathaving a pair I of contactors each adjustable individually todetermine apoint of balance of said bridge, whereby to preselect the limits ofmovement of said receiving rheostat contactor and said regulatingresistance contactor in opposite directions respectively, means forrendering said sending rheostat contactors effective selectively forpredetermined periods of time with reference to a given cycle, meansresponsive to unbalance of said bridge to selectively establish powerconnections for said motor to effect operation thereof in one directionor the other and tending to restore balance'of said bridge at one or theother of said points depending upon which of said sending rheostatcontactors is eflective, said last mentioned means comprising apolarized relay coil connected in said Wheatstone bridge circuit and acontactor associated with said coil, said contactor being normallybiased to an intermediate position and the same being movable by saidcoil in one direction or the other accorde ing to the sense of unbalanceof said bridge, a I

pair of contacts to be engaged by said contactor selectively uponmovement thereof in one direction orthe other, and means to preselectthe speeds of said motor for each direction of opera-v tion thereof. v

4. In an illumination control system, in combination, a lamp circuit,illumination intensity control means comprising a resistance elementincluded in said lamp circuit and a contactor movable with respect tosaid resistance element, a reversible electric motor for eflectingmovement of said contactor in one direction or the other, follow-upcontrol means for said motor coinprlsing a sending rheostat, a receivingrheostat and a polarized relay coil arranged in the form of a Wheatstonebridge, a contactor associated with said receiving rheostat and adaptedto be driven by said motor, a pair of contactors associated with saidsending rheostat, said last mentioned contactors being manuallyadjustable individually to determine a point of balance of saidbridge,-whereby to preselect the limits of movement of said receivingrheostat contac'torin opposite directions respectively, anelectromagnetically operable switch adapted when de-energized to rendereffective one of said sending rheostat contactors, said switch beingadapted when energized to altera V nativeiy render effective the otherof said sending rheostat contactors, means for sequentially effectingenergization and deenergization of said switch for predetermined periodsof time, a contactor associated with said polarized relay coil, saidcontactor being normally biased to an intermediate position and the samebeing movable by said coil in one direction ,or the other according tothe sense of unbalance of the Wheatstone bridge, a pair of contacts tobe engaged by said contactor selectively upon movement thereof in onedirection or the other, said contacts when entensity regulating'meansfor said lampsymeans for operating said regulating means between limitsdetermining the minimum and maximum values of intensity of illuminationof said lamps; said last mentioned means comprising a sending impedanceand receiving means connected with the latter in the form ofa balancingcontrol circuit, the balance of which determines the said limits ofoperation of said regulating means, said sending impedance having a pairof elements which are'selectively effective each to determine a point ofbalance of said circuit, whereby to select a minimum and a maximumintensity of illumination, respectively, for said lamps, associatedmeans operable by, unbalanceof said circuit automatically to restorebalance of said circuit at one or the other of said points dependingupon which of said elements is effective, and simultaneously to operatesaid regulating means to provide for sequential and gradual decrease orincrease in the intensity of illumination of said lamps; meansassociated with said last named restoring means to render the sameoperative at a predetermined rate during said decrease of intensity ofillumi-. nation and at a second predetermined rate during said increaseof intensity of illumination; and power operated'means to respectivelytime initiation of the decrease and the increase in said intensityof'illumination with reference to a given cycle'b'y rendering one or theother of said elements. eifective.

6. In an illumination control system, in cornbination, a groupofelectric lamps, illumination intensity regulating means for saidlamps, means for operating said regulating means between limitsdetermining the minimum and maximum values of intensity of illuminationof said lamps; said last mentioned means comprising a sending impedanceand follow-up means connected with the latter in the form of a balancingcontrol circuit, the balance of ,which determines the said limits ofoperation of said regulating means, said sending impedance having a pairof elements which are selectively effective each to determine a point ofbalance of said circuit, whereby to select a minimum and a maximumintensity of illumination, respectively, for said lamps, associatedmeans operable by unbalance of said circuit automatically to tend torestore balance of said circuit at one or the other of said pointsdepending upon-which of said elements is eifec- 'tive, andsimultaneously to provide for sequential and gradual. decrease orincrease'in the intensity of illumination of said lamps;means-associated with said last named restoring means to render the sameoperative at a predetermined rate during said decrease of intensity orillumination and .r

at a second predetermined rate during said increase of intensity ofillumination; and power operated means to respectively time initiationof the decrease and the increasein said intensity of illumination withreference to a given cycle by rendering said elements efiectivealternately, whereby to effect decrease and increase in the intensity ofillumination of said lamps between said minimum and maximum values in aregularly recurring cycle.

7 In an illumination control system, in combination, a group of electriclamps, illumination intensity regulating means for said lamps, means foroperating said regulating means between limits determining the minimumand maximumvalues of intensity of illumination of said lamps; said lastmentioned means comprising a sending impedance and receiving meansconnected with the latter to provide a balancing control circuit, thebalance of which determines the said limits of operation of saidregulating means, said sending impedance having a pair of elements whichare selectively eiiective each to determine a point of balance of saidcircuit, whereby to select a minimum and a maximum intensity ofillumination, respectively, for said lamps, associated means operable byunbalance of said circuit automatically to tend to restore balance ofsaid circuit at one or the other of said points depending upon which ofsaid elements is eiiective, and simultaneously to operate saidregulating means to provide for sequential and gradual decrease orincrease in the intensity of illumination of said lamps; meansassociated with the last named restoring means to render the sameoperative at a predetermined rate during said decrease of intensity ofillumination and at a second predetermined rate during said increase ofintensity of illumination, whereby to select the periods of dwell orunchanging minimum and max mum intensities of illumination of said lampswith respect to a given cycle; and power operated means to respectivelytime initiation of the decrease and the increase in said intensity ofillumination with reference to said cycle by rendering said elements 1effective alternately.

8. In an illumination control system, in combination, a plurality ofgroups of electric lamps, each of said groups of lamps havingillumination intensity regulating means individual thereto, each of saidregulating means having means tween limits determining the minimum andmaximum intensities of illumination of said group of lamps; said lastmentioned means comprising a sending impedance and receiving meansconnected with the latter to provide a balancing control circuit, thebalance of which determines the said limits of operation of saidregulating means, said sending impedance having a pair of elementswhichare selectively effective each to determ ne a point of balance ofsaid circuit, whereby to select a minimum and a maximum intensity ofillumination, respectively. for said group of lamps, associated meansoperable by unbalance of said circuit automatically to tend to restorebalance of said circuit at one or the other of saidpoints depending uponwhich of said elements is effective, and simultaneously to operate saidregulating means to provide for sequential and gradual decrease orincrease in the intensity of illumination of said group of lamps; meansassociated with the last named restoring 'rneans to render the sameoperative at a predetermined rate dur ing said decrease of intensity-orillumination and at a second predetermined rate during said increase ofintensity of illumination; and common power operated means includingadjustable parts associated with the said individual operating 'means torespectively time the initiation or the decrease and the increase insaid intensity of illumination with reference to a. given cycle byrendering one or the other of said elements eftective, whereby the.decreasing or increasing or unchangingintensities of illumination of therespective groups of lamps are controlled in a predeterminedrelationship.

.9. In an illumination control system, in combination, a plurality ofgroups of electric lamps, each of said groups of lamps havingillumination intensity regulating means individual thereto, each of saidregulating means having means associated therewith for operating thesame between limits determining the minimum and maximum values ofintensityof illumination of said group of lamps; said last mentionedmeans comprising a sending impedance and a receiving impedance connectedin parallel in the form of a Wheatstone bridge, the balance of whichdetermines the said limits of operation of,said regulating means, saidsending impedance having a pair of elements which are selectivelyeffective each to determine a point of balance of said bridge, wherebyto select a minimum and a maximum intensity of illumination,respectively, for said group of lamps, associated means operable byunbalance of said bridge automatically to tend to restore balance ofsaid bridge at one or the other of said points depending upon which ofsaid elements is eiiective, and simultaneously to operate saidregulatingmeans to provide for sequentialand gradual decrease or increase in theoperating means for said regulating means to respectively time theinitiation of the decrease and the increase in said intensity ofillumination with reference to a given cycle by rendering one or theother of said elements effective, whereby the decreasing or increasingor unchanging associated therewith for operating the same beiintensities of illumination of the respective groups of lampsareocontrolled in a predetermined rela tionship.

id. In an illumination control system, in corn bination, a plurality ofgroups of electric lamps, each oisaid groups of lamps havingillumination intensity regulating means individual! thereto, each oisaid regulating means having means associated therewith for operatingthe same between limits determining the minimum and maximum values ofintensity of illumination of said group of lamps; said last mentionedmeans comprising an electric valvehaving a grid and adapted to vary theimpedance oi said regulating means in accordance with the conductivityof said valve, as sending impedance having a pair of elements which areselectively effective each to determine a value of voltage to beimpressed upon said grid, whereby to select a minimum and a maximumintensity oi! illumination, respectively, for said group of lamps; meanshaving an inherent time function for effecting changes of said gridvoltage and thereby simultaneously to vary the impedance oi saidregulating means to provide for sequential and gradual decrease orincrease in the intensity of illumination of said group oi lamps betweeniii) said selected minimum and maximum values. means associated withsaid last named means to selectively modify the time function thereof,whereby to render the same operative at a predetermined rate during saiddecrease of intensity of illumination and at a second predetermined rateduring said increase of intensity of illumination; and common poweroperated means including adjustable parts individual to each of theoperating means for said regulating means to respectively time theinitiation of the decrease and the increase in said intensity ofillumination with reference to a given cycle by rendering said elementseffective alternately, whereby the decreasing or increasing orunchanging intensities of illumination of the respective groups of lampsare controlled in a like relationship for repeated cycles.

11. -In an illumination control system, .in combination, a group ofelectric lamps, illumination intensity regulating means for said lampscomprising a variable impedance device, means comprising an electricvalve having a control grid and adapted to vary the impedance of saidregulating means in accordance with the conductivity of said valvebetween limits determining the minimum and maximum values of intensityof illumination of said lamps, means for varying the conductivity ofsaid valve, said means comprising a sending impedance having a pair ofelements which'are selectively effective each to determine a value ofvoltage to be impressed upon said grid, whereby to select a minimum anda maximum intensity of illumination, respectively, for said lamps, meanshaving an inherent time function for effecting changes of said gridvoltage and thereby simultaneously to vary the im pedance of saidregulating means between said limits, means associated withsaid lastnamed means to selectively modify the time function thereof, whereby torender the same operative at a predetermined rate during said decreaseof intensity of illumination and at a second predetermined rate duringsaid increase of intensity of illumination; and power operated means torespectively time initiation oi the decrease and the increase in saidintensity of illumination with reference to a given cycle by renderingsaid elements effective selectively. v

12. In an illumination control system, in combination, a group ofelectric lamps, a variable impedance device for regulating theillumination intensity of said lamps, means for varying the impedance ofsaid device between limits determining the minimum and maximum values ofillumination intensity of said lamps; said last mentioned meansincluding an electric valve having a grid for controlling itsconductivity in accordance with the voltage impressed upon said grid,means comprising a sending impedance having a pair of elements which areselectively effective each to determine a value of voltage to beimpressed upon said grid, whereby to select a minimum and a maximumintensity of illumination, respectively, for said lamps, an energystorage circuit connected to said grid, andmeans having an inherent timefunction for controlling the changes in said grid voltage and therebysimultaneously varying the impedance of said device between the saidlimits, means associated with the last named means to selectively modifythe time function thereof, whereby to render the same operative at apredetermined rate during said decrease of illumination intensity and ata second predetermined rate during said increase of illuminationintensity; and power operated means to respectively time initiation ofthe decrease and the increase in said illumination intensity withreference to a given cycle by rendering one or the other of saidelements effective.

13. In an illumination control system, in combination, a source ofelectric power, an electric valve having a grid for controlling itsconductivity in accordance with the voltage impressed upon said grid, alamp circuit connected to said source and to said valve and whosevoltage varies in accordance with the conductivity of said valve, anenergy storage circuit connected to said grid having an inherent timefunction and adapted 'to vary the voltage impressed thereby upon saidgrid, and means comprising a plurality of energy storage circuits havingdifferent discharge characteristics which are selectively effective tomodify the time function of ,said first named storage circuit, wherebysaid grid voltage is varied at a selected rate.

14. In an illumination control system, in cor L'- bination, a group ofelectric lamps, illumination intensity regulating means for said lamps,means for operating said regulating means between limits determining theminimum and maximum values of intensity of illumination of said lamps,said last mentioned means comprising an electric valve having a grid andadapted to vary the impedance of said regulating means in accordancewith the conductivity of said valve, a sending impedance having a pairof elements which are selectively effective each to determine a value ofvoltage to be impressed upon said grid, whereby to select a minimum anda maximum intensity of illumination, respectively, for said lamps, anenergy storage circuit connected to said grid having an inherent timefunction and adapted to,

vary the voltage impressed upon said grid and thereby simultaneously tovary the impedance of said regulating means to provide for gradualdecrease or increase in the intensity of illumination of said lampsbetween said selected minimum and maximum values, means comprising aplurality of additional energy storage circuits having differentdischarge characteristics which are selectively effective to modify thetime function 'of said first mentioned energy storage circuit, wherebyto render the Latter operative at predetermined rates during thedecrease or the increase in the intensity of illumination, and poweroperated means to respectively time initiation of the decrease and theincrease in said intensity of i1- lumination with reference to a givencycle by sequentially rendering one and then another of said lastmentioned energy storage circuits effective.

RICHARD B. HUNTER.

